This invention relates to an infinitely adjustable elevating system for a treadmill.
Generally, exercising treadmills have come into widespread use for walking or running "in place" indoors to maintain a program of physical fitness or, in a medical testing facility, to permit patients undergoing a stress electrocardiogram test to exercise vigorously while electrocardographic and other data is acquired. Generally, exercise treadmills include a frame extending lengthwise of the treadmill having a pair of spaced apart side rails with a front and rear horizontal roller interposed therebetween and journaled with respect to the side rails. An endless treadmill belt is entrained around the rollers and the upper reach of the belt is supported by a bed or the like so as to constitute a walking or jogging surface which will support a user of the treadmill while walking or running thereon. The treadmill belt is driven by an electric motor or the like such that the upper reach of the belt moves from front to rear over the bed, thus necessitating a user of the treadmill to walk or run in forward direction on the moving belt so as to remain stationary with respect to the frame of the treadmill. Typically, the speed of the treadmill belt can be varied.
For a general description of such treadmills, reference may be made to our U.S. Pat. No. 4,616,822, issued Oct. 14, 1986, which is herein incorporated by reference.
In addition to increasing or decreasing the speed of the belt to vary the amount of physical exertion expended by a user of the treadmill, it is oftentimes typical for the treadmill to have an elevation system which selectively raises the front of the treadmill relative to the rear of the treadmill, thus inclining the jogging or walking surface such that a person walking or jogging on the upper reach of the treadmill belt will, in essence, be required to walk or run uphill, thus expending additional energy.
In U.S. Pat. No. 3,643,943, a treadmill elevating system is disclosed in which a gearmotor drives a single upright screw so as to raise and lower the front of the treadmill relative to the back of the treadmill. However, this elevating system requires a floor engaging base for mounting the electric motor, and a treadmill frame which is pivotally connected to the rear of the floor engaging base. Additionally, since only one gearmotor and screw is provided, the treadmill frame, when elevated, may not have a degree of stability which is desirable when an adult walks or jogs on the treadmill surface.
U.S. pat. No. 3,731,917 discloses a treadmill in which a pair of removable legs is provided at the front of the treadmill, with these legs being interchangeable with legs of different lengths so as to change the elevation of the treadmill.
U.S. Pat. No. 3,826,491 discloses a treadmill in which the frame of the treadmill, intermediate its ends, is pivotally mounted on a floor engaging base and in which a fluid operated cylinder at one end of the frame effects pivoting movement of the frame relative to the base so as to change the elevation of the treadmill.
U.S. Pat. No. 4,344,616 discloses the provision of a hand-operated screw jack at each side of the front of the treadmill frame which may be manually rotated in one direction or the other to change the elevation of the treadmill.
U.S. design pat. No. 270,555 also discloses an exercise treadmill having screw jacks at each side of the front of the frame, with the screw jacks being rotatable to vary the elevation of the treadmill.
U.S. design pat. No. 273,029 discloses an elevating system for a treadmill, in which legs at the front of the treadmill frame are pivotally mounted with respect to the treadmill frame may be rotatably, pivotally raised and lowered so as to change the elevation of the treadmill.